In the past decades, Lithium-ion battery (LIB) has been widely utilized in various applications especially consumer electronics, due to their superior energy density, long life type and discharging capability. Market has witnessed the tremendous increase since the first LIB was developed by SONY in 1991.
Lithium-ion batteries typically include an anode, an electrolyte, and a cathode that contains lithium in the form of a lithium-transition metal oxide, such as LiCoO2, LiNiO2 and LiMn2O4. Currently, lithium-ion batteries mostly utilize metal oxides as cathode material with LiCoO2 as the most popular and commercially successful representative. However, due to the intrinsic material properties of this cathode material, besides the toxicity and high material cost of cobalt, further enhancement of LIB performance is also limited. LiNiO2 is characterized for its high specific capacity up to 180 mAh/g. But its application is limited to experimental research because of difficulties in synthesis and safety concerns due to the thermal runaway reaction. LiMn2O4 has been considered as a promising cathode due to its advantages of high stability and low cost. However its low charge capacity and inferior cycling performance, especially under high temperatures, limit the application of this material to small electrokinetic cells.
In recent years, multi-element lithium transition metal oxides Li[NixMnyCo1−x−yO2]O2 (LNMC) and xLi2MnO3.(1-x)Li[NixMnyCo1−x−y]O2 or called “Lithium-rich layered oxide” (LLO) have been proposed to replace existing battery cathodes. While the LNMC ternary lithium metal oxide is expected to leverage merits of each component material and might even prevail in the overall performance, LLO has the potential to provide much higher specific capacity than existing cathode materials up to ˜300 mAh/g. Nevertheless, there are still some drawbacks in the multi-transition metal oxides cathode materials to be improved, for instance, phase transformation and thermal stability related safety issue for LNMC as well as the large irreversible first cycle capacity and fast deterioration of capacity after repeated charge and discharge cycles for LLO. Therefore, it is clear that existing single structured cathodes cannot deliver “perfect” performance for various application requirements. Tremendous efforts are still underway to develop new cathode or modify the existing structures for performance improvement or customization to fit the need of specific applications.
Conventional battery design is generally performed by an empirical approach. Designers propose specifications of a battery design, make batteries accordingly in a small research and development environment, and test the performance of the batteries. This process is iterated for incremental improvement of battery performances. Furthermore, the identified optimal design for one application usually does not apply to others. In other words, the whole empirical, iterative, costly and time-consuming design process needs to be repeated for different applications. Significant efforts are currently underway, mainly in the academic community and Department of Energy laboratories to use computer based computational methods simulations to accelerate the search for new and better materials for the battery industry. A major theme for much computational work has been the strong synergy with experimental studies. In literatures, density functional theory (DFT) has been used to predict the cell voltage changes and the battery charging/discharging behavior.
U.S. Patent Application No. US 2012/0130690 A1 describes a method and computer programs for selecting electrode material for a lithium ion battery. The invention discloses a general development approach for battery materials combining Quantum Simulation (QS) and equivalent circuit modeling and a database including the performance properties of typical electrode material structures. The microscopic material properties such as specific capacity for battery, cell voltage, lattice constants, lattice volume change and even X-ray diffraction (XRD) or Neutron Diffraction (ND) can be simulated by the developed algorithm and then the discharging behavior of a battery half-cell made from the electrode material can be derived from either the data obtained from QS calculation or from experiment. However this method is mainly limited to the fundamental material properties estimation without considering the parameters more related to the full-cell electrical behavior, such as electrode material packing density, lithium ion diffusivity in the active/inactive electrode materials, and lithium ion diffusion pathways. Furthermore, the method and databased disclosed in this invention focus only on the properties screening of given material structure and compositions without involving the need to simulate the modifications of given material such as doping and surface capping on the particulates.
U.S. Pat. No. 7,945,344 B2 describes a method to design a battery system for manufacturing by using a computational approach. A three dimensional model of battery comprising the basic battery element is built to correlating a series of electrical, thermal, mechanical, transport, or kinetic characteristics of the cell to the battery material properties such as the size, shape, composition and potential interface interactions. By optimizing the performance factors to the predetermined range, one or more required material properties including anode, cathode, separator and current collectors can be determined for manufacturing. However, this invention focuses only on the effects of material geometric and compositional factors in the battery cell structure as the guidance for battery manufacturing. No designing and optimization of the battery material structure is considered.
U.S. Pat. No. 8,301,285 B2 describes a method of designing and manufacturing a solid-state electrochemical battery cell for a battery device. A database including various materials for solid-state battery and their material properties are provided. Based on the target battery performance requirement, the battery materials including anode, cathode, electrolyte and separator are selected from the database with given material properties and then subjected to an optimization procedure by varying the battery geometric factors. This invention relates to an approach to determine design and manufacturing factors for solid-state battery cell by the given material property data, which is less correlated to the development for the typical lithium ion battery.
In view of the above, there is always a need to find ways for designing and improving electrode materials for electrochemical cells, which provides a holistic solution to develop lithium ion batteries for various applications.